Abstract.
The aim of this work is to present a tutorial on Multivariate Calibration, a tool which is nowadays necessary in basically most
laboratories but very often misused, The basic concepts of preprocessing, principal component analysis (PCA), principal
component regression (PCR) and partial least squares (PLS) are given, The two basic steps an any calibration procedure: model
building and validation are fully discussed, The concepts of cross validation (to determine the number of factors to be used in the
model), leverage and studentized residuals (to detect outliers) for the validation step are given, The whole calibration procedure is
illustrated using spectra recorded for ternary mixtures of 2,4,6-trinitrophenolate, 2,4-dinitrophenolate and 2,5-dinitrophenolate
followed by the concentration prediction of these three chemical species during a diffusion experiment through a hydrophobic liquid
membrane, MATLAB software is used far numerical calculations, Most of the commands for the analysis are provided in order to
allow a non-specialist to follow step by step the analysis.

Keywords.
Chemometrics; Multivariate Calibration; PLS; PCR; Liquid Membranes.

Keywords Plus.
Squares.